I returned to my day centre on Thursday for the first time since 17th December, and I was asked to wear a mask there all day (apart from when I was eating and drinking, obviously), and it didn't do me any harm. In fact, I got used to it in no time at all.
It was quite reassuring that mask-wearing co-operation from the other clients there was very high and none of them seemed to kick up a fuss over it nor questioned it in any way.